An al-Aqsa Martyrs Brigades spokesman told a news conference in Gaza that it was a joint operation between al-Aqsa, the Popular Front for the Liberation of Palestine (PFLP) and another lesser-known faction.

The group denied bombers Luai Aghwani and Musa Arafat, both from Khan Younis, had reached Israel from Egypt.

However, Mr Arafat's mother said her son had telephoned her from the Egyptian town of el-Arish.

A spokesman for Hamas, which controls Gaza, said the Dimona attack was "a natural reaction to months of killing" of Palestinians by the Israeli army.

He also criticised an earlier military raid in the northern West Bank earlier in the day in which Israeli commandos killed two Palestinian gunmen.

'Relentless war'

Israel was hit by series of suicide bombings in the 1990s and 2000s, peaking after the Palestinian intifada or uprising broke out in 2000.

However, there were only two such attacks between April 2006 and now, the last being in January 2007 when a bomber blew himself up in a bakery in Eilat, killing three people.

Monday's blast is also the first since renewed efforts to come to an Israeli-Palestinian peace deal were launched with US support last November.

Hours later, Israeli aircraft assassinated the top military commander of the Popular Resistance Committees, Amer Qarmut, alias Abu Said.

Prime Minister Ehud Olmert told a meeting of his Kadima party that Israel was fighting a "relentless war... against anyone who tries to harm Israeli citizens".

Israel argues that restrictions it imposes on about four million Palestinians in Gaza and large parts of the occupied West Bank are crucial in preventing such attacks, though the blockades have been condemned as "collective punishment" by the UN.